Persona.4.Arena.NTSC.XBOX360-iMARS
Region locked NA only by the looks of things, technically not out until Tuesday according to gamefaqs. PAL release due at the end of the month
The Japanese (region locked but English sporting release in Persona_4_The_Ultimate_in_Mayonaka_Arena_JPN_XBOX360-Caravan hit a few days back and there was a discussion thread.

From the UK amazon
Persona 4 Arena seamlessly integrates the elaborate characters and worlds of a JRPG with the exciting head to head combat of a fighting game. Set two months after Persona 4 – Persona Arena is a direct sequel and an adventure in its own right. Following Teddie's sudden disappearance in Inaba, his friends find what appears to be Teddie in a pirate outfit announcing a fighting tournament called the "P-1 Grand Prix" to see who is the "Ultimate Persona User". Bewildered by this turn of events, they band together once again and enter the tournament to find out what has happened to their friend, but end up being pitted in battle against each other.

Each character has their own unique story and path to unravel the mystery – told through all new anime sequences and scenarios written by the Persona Team.

Features:

13 characters in total including Persona 3 fan favourites – and the chance to catch up on their stories since their last appearance!
Full Persona 4 cast returns, including Yosuke, Kanji, Naoto and Teddie – and will feature the original voice actors.
Each character has their own “Persona” – a secondary character that can be called into battle to unleash deadly attacks!

Characters and Persona together, allow for a fighting experience like no other

Twin Health gauges for Persona and Characters add new layer of strategy.
Dual character system allows you to wield two characters simultaneously!
Effortlessly link both Persona and Character attacks into spectacular combos.

A battle experience designed for fans of the RPGs as well as fighting game enthusiasts

Character and Persona details, moves and specials lifted directly from Persona.
Status effects, like poison, confusion, paralysis and fear – just like the RPG!
Substantial story, dialogue and anime further exploring the world and characters.

Genuinely accessible fighting caters for all skill levels at the same time.

Innovative single button combo system allows everyone to compete at a high level.
Simpler special move inputs allow you to concentrate on the thrill of competitive play and strategy – not the execution of moves.
Become progressively more powerful the closer you are to being knocked out!
More ways to interrupt combos – allowing novices more opportunity to counter-attack.
Introduction of a ‘dodge’ function to move away from over reliance on blocking.

A wide variety of game modes

Story Mode: Pick a character and discover their story through mystery of the Midnight Channel.
Arcade Mode: Classic Arcade action. Fight each character in turn, in progressively difficult battles.
Score Attack: A series of battles against tough opposition, where battling with speed and finesse is key!
Training: Practice your combos against a CPU opponent that can be fine-tuned to your preferences.
Lesson: Superb step by step introduction to all the fighting system’s key features and techniques.
Challenge: The perfect introduction to learning your own combos - both easy and advanced.
Versus: Two player mode where you can fight a friend or CPU opponent offline.
Network: Pit your skills against the best the world has to offer by taking your game online.
Contents Market: Online marketplace where you will be able to purchase and download DLC.
Replay Theatre & Gallery Mode: Unlock exclusive artwork, music or watch and save your greatest battles!

Video E3 trailer

BoxartThe prospective EU boxart looks quite different but that will be covered when a PAL compatible release appears